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ISRN Corrosion
Volume 2012 (2012), Article ID 937920, 9 pages
Research Article

Black Wattle Tannin As Steel Corrosion Inhibitor

1Laboratório de Eletroquímica, Instituto de Química, UFRGS, Avenida Bento Gonçalves 9500, 90619-900 Porto Alegre, RS, Brazil
2Departamento de Engenharia Química, Faculdade de Engenharia, PUCRS, Avenida Ipiranga 6681, 90619-900 Porto Alegre, RS, Brazil

Received 31 January 2012; Accepted 22 February 2012

Academic Editors: L. Bazzi, G. Bereket, A. Kalendová, and E. E. Oguzie

Copyright © 2012 Rafael Silveira Peres et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In order to reduce the environmental impacts caused by chemical substances harmful to the environment and human health, the black wattle tannin can be used as an environmentally friendly corrosion inhibitor in acid and near neutral media. This paper provides information on the application of black wattle tannin as an inhibitor against the corrosion of carbon steel. The inhibition was evaluated using potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) at room temperature in aerated 0.1 mol L−1 Na2SO4 (pH 6.0 and 2.5). The black wattle tannin when used as a corrosion inhibitor is more effective at acidic pH, its efficiency being dependent on its concentration. At the higher pH value (pH 6.0), a blue-black film (ferric tannate) with a short-term protection against corrosion was formed in aerated aqueous solution. At pH 2.5, this blue-black film was not observed.